Earthmoving and construction vehicles, especially self-laying track-type vehicles, generate considerable noise during traveling and operation of the vehicle. Such noise is not only objectionable to nearby workers and spectators, but is especially bothersome to the vehicle operator. The vehicle operator is closest to the noise and generally operates the vehicle many hours a day. Any reduction in the vehicle noise reaching the operator will help reduce operator fatigue, which will make the operator more alert and productive. One way to reduce the noise level reaching the vehicle operator is to install a sound barrier in the overhead cover of the operator's station. Various types of sound barriers have been used in the past, and various means have been utilized to fasten the barriers to the overhead cover.
One type of barrier is described in U.S. Pat. No. 4,097,085, issued June 27, 1978, to A. E. Nelson. The dome-shaped barrier described in this patent has an upper support portion of rigid construction, such as fiberboard, and a lower sound absorbing portion, such as carpeting. A plurality of holes are drilled through both the upper and lower portions. These holes allow the air from the air conditioner to enter the interior of the cab. The exact details of how the barrier is secured in place are not disclosed. Although this barrier would appear to distribute the air from the air conditioner into the cab interior, it would seem to have poor sound-barrier qualities because of the many through holes.
U.S. Pat. No. 4,069,738, issued Jan. 24, 1978, to R. D. McClure discloses an insulation retainer and a method of securing insulating material against a plate using the retainer. The method of retaining the insulating material in place includes a plurality of holes through the plate, such holes being filled with a deformable plug. Each plug holds a pointed stud which extends out of the plug. The insulating material is pushed over the plurality of studs, such studs piercing the insulating material. A protective cap is then fitted over each of the projecting studs to firmly hold the insulating material in place. Although this retainer method is typical of prior art practices for retaining insulation and sound barriers in earthmoving and construction vehicles, it does require considerable time, materials, and effort.
The present invention is directed to overcoming one or more of the problems as set forth above.